Pneumatic valve control having improved opening characteristics and an air turbine starter incorporating the same

ABSTRACT

A starter air valve assembly includes a valve body, a flow control valve, a rate control servo mechanism, and a valve actuator. The valve body defines a flow passage having at least an inlet port and an outlet port. The valve is disposed at least partially within the flow passage and is moveable between an open position and a closed position. The rate control servo mechanism is adapted to receive pressurized fluid and is configured, upon receipt thereof, to supply a controlled flow of the pressurized fluid. The valve actuator is coupled to the valve and is in fluid communication with the rate control servo to thereby receive the controlled flow of the pressurized fluid. The valve actuator is configured, upon receipt of the controlled flow of the pressurized fluid, to move the valve between the closed position and the open position at a substantially controlled rate.

TECHNICAL FIELD

The present invention relates to pneumatically actuated valves and, moreparticularly, to a pneumatically actuated starter air valve havingimproved opening characteristics.

BACKGROUND

Many relatively large turbine engines, including turbofan jet engines,may use an air turbine starter (ATS) to initiate turbine enginerotation. The ATS may be mounted by the engine, much as a starter for anautomobile is located by the automobile engine. The ATS may be coupledto a high pressure fluid source, such as compressed air, which impingesupon a turbine wheel in the ATS causing it to rotate at a relativelyhigh rate of speed. The ATS includes an output shaft that is coupled tothe turbine wheel and, perhaps via one or more gears, to the jet engine.The output shaft thus rotates with the turbine wheel. This rotation inturn causes the jet engine to begin rotating. The applicant for thepresent invention, Honeywell International, Inc., has for yearssuccessfully designed, developed, and manufactured ATSs.

The flow of compressed air to an ATS may be controlled by, for example,a valve. This valve, if included, is typically referred to as a starterair valve. When the starter air valve is open, compressed air may flowthrough the starter air valve, and into the ATS. Conversely, when thestarter valve is closed, compressed air flow to the ATS may beprevented. An ATS starter air valve, in many instances, includes apneumatic actuator to move the valve into its open position. The sourceof pneumatic power to the actuator may be pressurized air supplied from,for example, an auxiliary power unit (APU), bleed air from anotherengine compressor, or a ground cart. In some instances, the pressurizedair supplied to the ATS and the starter air valve is non-regulated, andat a pressure magnitude greater than what may be needed for the ATSoperation. Hence, some aircraft starter air valves may also beconfigured as a pressure regulating valve, to thereby regulate thepressure of the air flow to the ATS.

Many starter air valve pneumatic actuators, for both regulator andnon-regulator types of valves, include pistons with either a dynamicseal or diaphragm. Many of these actuators also include a small,fixed-diameter rating orifice to help control the opening rate of thestarter air valve, and the pressure rise rate downstream of the starterair valve. Although these present actuators generally operate safely andeffectively, the actuators can suffer certain drawbacks. For example,the piston seal (or diaphragm) can wear and cause some leakage past theactuator piston. This leakage can potentially degrade the openingperformance of the starter air valve. In some cases, if the leakagebecomes great enough, the actuator may be unable to open the starter airvalve.

Hence, there is a need for a pneumatic control for various valves,including starter air valves, that addresses the above-noted drawbacks.Namely, a pneumatic control that will compensate for piston seal ordiaphragm leakage that may occur in the actuator and/or will continue tooperate even for relatively large amounts of piston seal or diaphragmleakage. The present invention addresses one or more of these needs.

BRIEF SUMMARY

The present invention provides a pneumatic valve assembly including acontrol that provides improved valve opening characteristics as comparedto presently known valve assemblies, and that compensates for certaintypes of leakage within the actuator.

In one embodiment, and by way of example only, an air starter valveincludes a valve body, a flow control valve, a rate control servomechanism, and a valve actuator. The valve body defines a flow passagehaving at least an inlet port and an outlet port. The valve is disposedat least partially within the flow passage and is moveable between anopen position and a closed position. The rate control servo mechanism isadapted to receive pressurized fluid and is configured, upon receiptthereof, to supply a controlled flow of the pressurized fluid. The valveactuator is coupled to the valve and is in fluid communication with therate control servo to thereby receive the controlled flow of thepressurized fluid. The valve actuator is configured, upon receipt of thecontrolled flow of the pressurized fluid, to move the valve between theclosed position and the open position at a substantially controlledrate.

In another exemplary embodiment, a rate control servo mechanism forcontrolling a rate of movement of a valve includes a housing, adiaphragm, a control air flow passage, a pre-charge flow passage, afeedback flow passage, a rate control flow passage, and a rate controlvalve. The housing defines at least a first chamber and a secondchamber. The diaphragm is disposed between the first and second chambersand fluidly isolates the first and second chambers from one another. Thecontrol air flow passage extends through the housing and has at least aninlet port and an outlet port. The control air flow passage inlet portis adapted to receive a flow of pressurized fluid, and the control airflow passage outlet port is fluidly coupled to the valve actuator. Thepre-charge flow passage is coupled to the housing and has at least aninlet port and an outlet port. The pre-charge flow passage inlet port isfluidly coupled to the control air flow passage, and the pre-charge flowpassage outlet port is in fluid communication with the second chamber.The feedback flow passage is coupled to the housing and has at least aninlet port and an outlet port. The feedback flow passage inlet port isadapted to fluidly couple to a flow duct, and the feedback flow passageoutlet port is in fluid communication with the second chamber. The ratecontrol flow passage is coupled to the housing and has at least an inletport and an outlet port. The rate control flow passage inlet port isfluidly coupled to the feedback flow passage outlet port, and the ratecontrol flow passage outlet port is in fluid communication with thefirst chamber. The rate control valve is disposed within the housing andis coupled to the diaphragm. The rate control valve is movable between aclosed position, in which the control air flow passage inlet port isfluidly isolated from the control air flow passage outlet port, and anopen position, in which the control air flow passage inlet port isfluidly coupled to the control air flow passage outlet port.

In yet another exemplary embodiment, an air turbine starter, includes aturbine housing, a turbine wheel, and a starter air valve assembly. Theturbine housing has a fluid inlet port, a fluid outlet port, and a fluidflow passage extending therebetween. The turbine wheel has a turbineshaft rotationally mounted within the turbine housing. The turbine wheelfurther includes at least two turbine blades that extend radially intothe fluid flow passage. The starter air valve assembly is coupled to theturbine housing and includes a valve body, a flow control valve, a ratecontrol servo mechanism, and a valve actuator. The valve body defines aflow passage that has at least an inlet port adapted to received a flowof pressurized fluid, and an outlet port in fluid communication with theturbine housing fluid inlet port. The flow control valve is disposed atleast partially within the valve body flow passage and is moveablebetween an open position and a closed position. The rate control servomechanism is adapted to receive pressurized fluid and is configured,upon receipt thereof, to supply a controlled flow of the pressurizedfluid. The valve actuator is coupled to the valve and is in fluidcommunication with the rate control servo to thereby receive thecontrolled flow of the pressurized fluid. The valve actuator isconfigured, upon receipt of the controlled flow of the pressurizedfluid, to move the valve between the closed position and the openposition

In yet a further exemplary embodiment, a method of opening a flowcontrol valve mounted on a valve body that defines a flow passagetherethrough, and that is coupled to a fluid-operated actuator coupledto the flow control valve includes supplying pressurized fluid to thefluid-operated actuator to generate an opening force that begins openingthe flow control valve, whereby pressurized fluid may flow through thevalve body flow passage. In response to fluid flow through the valvebody, the pressurized fluid is intermittently supplied to the actuatorto thereby intermittently generate the opening force at a controlledrate, whereby the flow control valve further opened at a controlledrate.

Other independent features and advantages of the preferred valveassembly, air turbines starter, and associated method will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section view of an exemplary air turbine starter thatmay be coupled to a starter air valve according to an exemplaryembodiment of the present invention;

FIG. 2 is a schematic representation of an exemplary embodiment of apneumatic valve that may be used as the starter air valve shown in FIG.1; and

FIG. 3 is a schematic representation of another exemplary embodiment ofa pneumatic valve.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any theory presented in the preceding background of theinvention or the following detailed description of the invention. Inthis regard, before proceeding with the detailed description, it shouldbe appreciated that the present invention is not limited to use inconjunction with a specific type of valve. Thus, although the presentinvention is, for convenience of explanation, depicted and described asbeing implemented in a pneumatically-operated butterfly valve and an airturbine starter, it should be appreciated that it can be implemented innumerous other types of pneumatic valves, and in various other devicesand environments in which pneumatic valves are used.

Turning now to the description, and with reference first to FIG. 1, across section view of an exemplary air turbine starter (ATS) that may beused to initiate the rotation of a larger turbine, such as a turbofanjet engine, is shown. The ATS 100 includes a housing assembly 102 thatis used to house various components. The housing assembly 102 may bemade up of two or more parts that are combined together or may beintegrally formed as a single piece. In the depicted embodiment, thehousing assembly is made up of a turbine section 104 and an outputsection 106.

The housing assembly turbine section 104 includes an inlet plenum 108,which directs pressurized air from a pressurized air source (notillustrated) into the housing assembly 102, via a starter air valve 200,which, for ease of illustration, is depicted schematically in FIG. 1. Itwill be appreciated that the pressurized air source may be any one ofnumerous known sources for supplying pressurized air to an ATS 100. Forexample, the non-illustrated pressurized air source could be anauxiliary power unit, bleed air from another operating gas turbineengine, or a gas turbine ground power cart. It will additionally beappreciated that a preferred embodiment of the starter air valve 200will be described in more detail further below.

No matter the specific source of the pressurized air, if the starter airvalve 200 is open, pressurized air is directed into the inlet plenum108, flows through an annular flow channel 110, and exits the ATS 100via a radial outlet port 112. The annular flow channel 110 includes anaxial flow portion 114 and a substantially curved radial flow portion116. The axial flow portion 114 is formed through a stator assembly 118that is mounted within the housing assembly turbine section 104proximate the inlet plenum 108. The radial flow portion 116, whichflares the annular flow channel 110 radially outwardly, is formedbetween a portion of the housing assembly turbine section 104 and anexhaust housing 120 that is mounted within the housing assembly 102.

A turbine wheel 122 is rotationally mounted within the housing assemblyturbine section 104. In particular, the turbine wheel 122 has an outputshaft 124 that extends from a hub 126, through the exhaust housing 120,and into the housing assembly output section 106. The turbine wheeloutput shaft 124 is rotationally mounted in the housing assembly outputsection 106 by bearing assemblies 128. A gear 132 is coupled to theturbine wheel output shaft 124, and meshes with a compound planetarygear train 134. The compound planetary gear train 134 engages a ringgear 138 and a hub gear 142, which is in turn coupled to an overrunningclutch 144. During operation of the ATS 100, this gearing configurationconverts the high speed, low torque output of the turbine wheel outputshaft 124 into low speed, high torque input for the overrunning clutch144.

The overrunning clutch 144, as noted above, is coupled to the hub gear142, which is supported by another bearing assembly 146. A drive shaft148 extends from the overrunning clutch 144, through the turbine housingoutput section 106, and is coupled to a turbine output shaft 152. Theoutput shaft 152 is in turn coupled to a turbofan jet engine via, forexample, a gearbox 154.

Turning now to FIG. 2, a detailed schematic representation of anexemplary embodiment of the starter air valve 200 is shown and will bedescribed in detail. The starter air valve 200 includes a valve body202, a flow control valve 204, an actuator 206, a rate control servomechanism 208, and an actuation control valve 210. The valve body 202 isadapted to be coupled, and to selectively provide fluid communication,the non-illustrated pressurized air source and the ATS inlet plenum 108(not shown in FIG. 2). In particular, the valve body 202 defines a flowpassage 212 having a fluid inlet port 214 adapted to couple to thenon-illustrated pressurized air source, and a fluid outlet port 216adapted to couple to the ATS inlet plenum 108.

The flow control valve 204 is disposed within the flow passage 212 andis moveable between a closed position and an open position, to therebycontrol pressurized air flow through the flow passage 212. In the closedposition, which is shown in FIG. 2, the flow control valve 204 preventspressurized air flow from the fluid inlet port 212, through the flowpassage 212, to the fluid outlet port 216. Conversely, when the valve202 is in the open position, pressurized air may flow through the flowpassage 212. The flow control valve 204 may be any one of numerous typesof valves useful to selectively isolate an upstream pressurized fluidsource from a downstream component. In the preferred embodiment,however, the flow control valve 204 is a butterfly valve.

The actuator 206 is coupled to the flow control valve 204 and isconfigured to selectively move the flow control valve 204 between theopen and closed positions. In the depicted embodiment, the actuator 206includes an actuator housing 218, a piston 220, and a piston bias spring222. The actuator housing 218 includes a fluid inlet port 224 and afluid outlet port 226. The fluid inlet port 224 is in fluidcommunication with the rate control servo mechanism 208, which isdescribed further below, and the fluid outlet port 226 is vented toambient surroundings.

The piston 220 is movably mounted within the actuator housing 218 and,in the depicted embodiment, is coupled to the flow control valve 204 viaa plurality of connection links 228, 230. Movement of the piston 220causes translation of one of the connection links 228, which in turncauses rotation of the other connection link 230. The rotatingconnection link 230 moves the flow control valve 204 between the openand closed positions. A plurality of seals 232 a, 232 b are coupled tothe piston 220 and fluidly isolate the actuator housing fluid inlet 224and outlet 226 ports from one another. The piston bias spring 222 isalso mounted within the actuator housing 218 and is configured to biasthe piston 220 in a direction that moves the flow control valve 204 toits closed position. Thus, it will be appreciated that the piston biasspring 222 also biases the flow control valve 204 toward the closedposition. Using the frame of reference provided by FIG. 2, the pistonbias spring 222 biases the piston 220 upwardly, though it will beappreciated that this is merely illustrative.

The rate control servo mechanism 208 includes a housing 234, a diaphragm236, a poppet valve 238, a valve bias spring 240, and a check valve 242.The housing 234 includes four inlet flow passages, and one outlet flowpassage. In particular, the housing 234 includes a control air inletflow passage 244, a pre-charge inlet flow passage 246, a feedback inletflow passage 248, a rate control inlet flow passage 250, and a controlair outlet flow passage 252. The control air inlet flow passage 244 iscoupled to receive a flow of pressurized air from the non-illustratedpressurized air source, the pre-charge inlet flow passage 246 is influid communication with the control air outlet flow passage 252, thefeedback inlet flow passage 248 and the rate control inlet flow passage250 are each in fluid communication with the valve body flow passage 212downstream of the flow control valve 204, and the control air outletflow passage 252 is in fluid communication with the actuator housingfluid inlet port 224.

In the depicted embodiment, it is seen that the pre-charge inlet flowpassage 246, the feedback inlet flow passage 248, the rate control inletflow passage 250, and the control air outlet flow passage 252 eachinclude a flow restricting orifice. In particular, the pre-charge inletflow passage 246 includes a pre-charge orifice 254, the feedback inletflow passage 248 includes a feedback orifice 256, the rate control inletflow passage 250 includes a rate control orifice 258, and the controlair outlet flow passage 252 includes a snubbing orifice 260. Thefunction of the snubbing orifice 260 is generally known and willtherefore not be further described. The function of the remaining threeorifices 254, 256, 258 will be described in more detail further below.

As FIG. 2 additionally shows, the rate control servo mechanism housing234, in combination with the diaphragm 236, defines two chambers—a firstchamber 262, and a second chamber 264. The diaphragm 236 is disposedbetween, and fluidly isolates, the first chamber 262 from the secondchamber 264. In a particular preferred embodiment, this is accomplishedby coupling the diaphragm 236 to the housing 234 and to a back plateassembly 266. No matter the particular manner in which this isaccomplished, the result is that the first chamber 262 is in fluidcommunication with the rate control inlet flow passage 256, and thesecond chamber 264 is in fluid communication with the feedback inletflow passage 248 and the pre-charge inlet flow passage 246. The purposeand function of these two chambers 262, 264 will become apparent whenoperation of the starter air valve 200 is described in more detailfurther below.

The poppet valve 238 is mounted at least partially within the ratecontrol servo mechanism housing 234, and is movable between an openposition and a closed position. In the open position, which is shown inFIG. 2, the control air inlet flow passage 244 is fluidly coupled to thecontrol air outlet flow passage 252 and the pre-charge inlet flowpassage 246. Conversely, when the poppet valve 238 is in the closedposition, the control air inlet flow passage 244 is fluidly isolatedfrom the control air outlet flow passage 252 and the pre-charge inletflow passage 246. Thus, if the control air inlet flow passage 244 is influid communication with a pressurized air source, and the poppet valve238 is open, pressurized air flows through the rate control servomechanism 208, out the control air outlet flow passage 252, and iscommunicated to the actuator having fluid inlet port 224. As will bedescribed in more detail further below, when the poppet valve 238 isopen, pressurized air may, under certain circumstances, also flowthrough the pre-charge inlet flow passage 246, and into the secondchamber 264. It will be appreciated that although a poppet valve is usedin the rate control servo mechanism 208, this is merely exemplary of aparticular preferred embodiment, and numerous other types of valvescould also be used.

No matter the specific type of valve that is used, the valve 238 isbiased toward its open position by the bias spring 240. In the depictedembodiment, the bias spring 240 is disposed within the housing firstchamber 262, between the housing 234 and the back plate assembly 266.The back plate assembly 266, as was noted above, retains a portion ofthe diaphragm 236. In addition, the back plate assembly 266 is operablycoupled to the poppet valve 238. The bias spring 240 is configured suchthat it exerts a downward bias force (as referenced to FIG. 2) againstthe back plate assembly 266, which is transmitted to the poppet valve238, thereby biasing the poppet valve 238 to its open position.

The check valve 242 is also disposed within the rate control servomechanism housing 234. More specifically, the check valve 242 isdisposed within the housing second chamber 264. The check valve 242 isconfigured to selectively fluidly couple the housing second chamber 264and control air outlet flow passage 252, depending on the differentialpressure across the check valve 242. In particular, the check valve 242is configured such that it is normally seated against the pre-chargeflow passage outlet port 268, thereby isolating the housing secondchamber 264 from the control air outlet flow passage 252. However, if aslight differential pressure exists across the check valve 242 (e.g.,less than about 1.0 psid), such that the pressure in the housing secondchamber 264 is less than that on the pre-charge flow passage outlet port268, the check valve 242 opens.

Turning now to a description of the actuation control valve 210, it isseen that this component includes a housing 270, a solenoid 272, a valve274, a valve bias spring 276, and solenoid bias spring 278. Theactuation control valve housing 270 includes an inlet flow passage 280,a fluid outlet passage 282, and a vent port 284. The actuation controlvalve housing inlet flow passage 280 is in fluid communication with thenon-illustrated pressurized air source. In the depicted embodiment, thecontrol valve housing inlet flow passage 280 is in fluid communicationwith the valve body flow passage 212 upstream of the flow control valve204, which is in turn in fluid communication with the non-illustratedpressurized air source. The actuation control valve housing outlet flowpassage 282 is in fluid communication with the rate control servomechanism housing control air inlet flow passage 244.

The valve 274 is mounted within the actuation control valve housing 270and is movable between a first position and a second position. In thedepicted embodiment, the valve 274 is a double ball type valve, thoughit will be appreciated that this is merely exemplary of a particularpreferred embodiment, and that various other types of valves could beused. No matter the particular type of valve used, in the depictedembodiment it is seen that the valve bias spring 276 biases the valve274 toward the first position (shown in FIG. 2). When the valve 274 isin the first position, the control valve housing fluid outlet passage282 is fluidly coupled to the vent port 284. When the valve 274 is inthe second position, the control valve housing fluid outlet passage 282is fluidly isolated from the vent port 284, and is fluidly coupled tothe control valve housing fluid inlet passage 280. As will be describedin more detail further below, when the valve 274 is moved from the firstto the second position, the end result is that the flow control valve204 will open. In addition, when the valve 274 is subsequently movedfrom the second position to the first position, the end result is thatthe flow control valve 204 will close.

The solenoid 272 is coupled to, or mounted within, the actuation controlvalve housing 270, and includes one or more coils 286, and a moveablearmature 288. As is generally known, when a solenoid coil 286 isenergized, it generates a magnetic force that acts on the armature 288,causing it to move. In the depicted embodiment, the solenoid 272 isconfigured such that when the solenoid coil 286 is energized, thearmature 288 moves the valve 274, against the bias force of both thesolenoid bias spring 278 and the valve bias spring 276, to the secondposition.

Having described the starter air valve assembly 200 from a structuralstandpoint, a description of how the starter air valve assembly 200functions, will now be provided. In the following discussion, it ispresumed that the flow control valve 204 is initially in the closedposition.

In order to open the flow control valve 204, to thereby permit fluidflow through the conduit 202, the actuation control valve solenoid 272is energized. When energized, the solenoid 272 moves the valve 274 fromthe first to the second position, thereby allowing pressurized air toflow through the actuation control valve 210 and into the rate controlservo mechanism control air inlet flow passage 244. Because the poppetvalve 238 is biased toward its open position, the pressurized air flowspast the poppet valve 238, into and through the control air outlet flowpassage 252 and the snubbing orifice 260, and into the actuator housing218. The pressurized air supplied to the actuator housing 218 causes theactuator piston 220 to begin to move the flow control valve 204 towardthe open position. As a result, pressurized air flows into the valvebody flow passage 212 downstream of the flow control valve 204, and thedownstream pressure begins to increase.

It will be appreciated that the pressure in the rate control servomechanism second chamber 264 is initially equal to the pressuredownstream of the closed flow control valve 204. Thus, at the same timethat pressurized air is supplied to the actuator housing 218,pressurized air also flows into the second chamber 264, via thepre-charge flow passage 246 and the check valve 242. This flow ofpressurized air begins pressurizing the second chamber 264 at a ratethat depends, at least in part, on the size of the pre-charge orifce254. When the pressure in the second chamber 264 reaches a predeterminedmagnitude, the pressure acts on the diaphragm 236 and back plateassembly 266, causing these components to move the poppet valve 238 tothe closed position. The increased pressure in the second chamber 264also acts on the check valve 242, causing it to close and fluidlyisolate the pre-charge flow passage 246 from the second chamber 246.

As the pressurized air begins flowing into the flow passage 212downstream of the flow control valve 204, some of the pressurized airflows into the feedback inlet flow passage 248. A portion of thispressurized air is directed into the second chamber 264, whereby thepressure in the second chamber 264 is essentially equal to the pressurein the flow passage 212 downstream of the flow control valve 204. Theremaining portion of the flow into the feedback flow passage 248 isdirected into the first chamber 262, via the rate control inlet flowpassage 250. The flow of pressurized air into the first chamber 262 isslowed by the rate control orifice 258, such that the pressure in thefirst chamber 262 rises at a controlled rate, and results in adifferential pressure between the first 262 and second 264 chambers.

When the pressure differential between the first 262 and second 264chambers rises to a predetermined magnitude, the pressure differentialacts on the diaphragm 236 and backing plate assembly 266, causing thesecomponents to move the poppet valve 238 toward the closed position.Conversely, when the pressure differential between the first 262 andsecond 264 chambers drops below the predetermined magnitude, thepressure differential acts on the diaphragm 236 and backing plateassembly 266, causing these components to move the poppet valve 238toward the open position. As the poppet valve 238 opens and closes, itmodulates the flow of pressurized air to the actuator housing 218.

The flow of pressurized air to the actuator housing 218 controls therate of motion of the piston 220, which controls the motion of the links228, 230, which in turn controls the rate of opening of the flow controlvalve 204. The rate of opening of the flow control valve 204 controlsthe rate of pressure increase in the flow passage 212 downstream of theflow control valve 204.

It will be appreciated that the relative sizes of the pre-charge orifice254, the feedback orifice 256, and the rate control orifice 258 areselected to achieve the desired valve opening characteristics. Inparticular, the pre-charge orifice 254 and feedback orifice 256 aresized relative to one another so that, as was noted above, the checkvalve 242 remains closed following the initial movement of the flowcontrol valve 204. The relative sizes of the pre-charge orifice 254 andfeedback orifice 256 are also selected to either minimize, or completelyeliminate, the previously mentioned pressure spike following initialopening of the flow control valve 204. The location of the feedbackorifice 256 in the schematic will cause the pressures in the firstchamber 262 and the second chamber 264 to equalize at steady state whenthe flow into the second chamber 264 is supplied by the pre-charge flowpassage outlet port 268. In addition, the feedback orifice 256 and ratecontrol orifice 258 are sized relative to one another so that thepressure in the second chamber 264 equalizes with flow passagedownstream pressure before the pressure in the first chamber 262, tomaintain a pressure differential between the first 262 and the second264 chmabers. As a result, the poppet valve 238 will modulate and theflow control valve 204 will open at a desired rate.

When it is desired to close the starter air valve 200, the actuationcontrol valve solenoid 272 is de-energized. As a result, the solenoidbias spring 278 and the valve bias spring 276, move the valve 274 to thefirst position. With the valve 274 in the first position, the actuationcontrol valve housing vent port 284 is fluidly coupled to the outletflow passage 282, which is in turn fluidly coupled to the rate controlservo mechanism housing control air inlet flow passage 244. Because thepoppet valve 238 is biased toward its open position, the control airoutlet flow passage 248 and thus the actuator housing 218 are fluidlycoupled to the control air inlet flow passage 244. Thus, the control airin the actuator housing 218 is vented to atmosphere via the actuationcontrol valve housing vent port 284. This releases the pressure on theactuator piston 220 and, assisted by the force of the actuator biasspring 222, causes the actuator 206 to move the flow control valve 204to the closed position.

As was previously noted, some starter air valves may be configured aspressure regulating valves. A particular embodiment of a pressureregulating starter air valve 300, is shown schematically in FIG. 3 andwill now be described in more detail. It will be appreciated that likereference numerals in FIG. 3 refers to like parts in FIG. 2. It is seenfrom FIG. 3 that the starter air valve 300 includes many of the samecomponents as the previously described starter air valve 200 embodiment.Thus, for brevity, the like components of these two embodiments will notbe once again described.

In addition to the previously described valve body 202, flow controlvalve 204, actuator 206, rate control servo mechanism 208, and actuationcontrol valve 210, the starter air valve 300 of FIG. 3 includes areference pressure regulator 302, a shuttle valve 304, and a bleed flowpassage 306. The reference pressure regulator 302 will be describedfirst, and is seen to include a housing 308, a regulator valve 310, adiaphragm 312, and a reference spring 314. The housing 308 includes aninlet flow passage 316, an outlet flow passage 318, and a vent 320. Theinlet flow passage 316 is in fluid communication with thenon-illustrated pressurized air source. In the depicted embodiment, theinlet flow passage 316 is in fluid communication with the flow passagefluid inlet port 214, which is in turn in fluid communication with thenon-illustrated pressurized air source. The outlet flow passage 318 isin fluid communication with the actuation control valve housing inletflow passage 280, and with the shuttle valve 304.

The diaphragm 312 is disposed within the regulator housing 308 and, incombination therewith, defines a vent chamber 322 and a referencepressure chamber 324 therein. The housing inlet 316 and outlet 318 flowpassages are in fluid communication with the reference pressure chamber324, and the vent 320 is in fluid communication with the vent chamber322. The diaphragm 312 in the reference pressure regulator 302, similarto the diaphragm 236 in the rate control servo mechanism 208, is coupledto the regulator housing 308 and to a back plate 326. The back plate 326is in turn coupled to the regulator valve 310.

The regulator valve 310 is mounted within the reference pressureregulator housing 308 and is moveable between a closed position and anopen position. In the closed position, the regulator valve 310 isolatesthe regulator housing outlet flow passage 318 from the inlet flowpassage 316. Conversely, when the regulator valve 310 is in the openposition, the regulator housing outlet flow passage 318 is fluidlycoupled to the inlet flow passage 316, and pressurized air may thus flowthrough the housing 308.

The reference spring 314 is disposed within the regulator housing ventchamber 320, and is coupled between the regulator housing 308 and theback plate 326. The reference spring 314 is configured to supply a biasforce to the regulator valve 310, via the back plate 326. The magnitudeand direction of the bias force supplied by the reference spring 314 issuch that it urges the regulator valve 310 toward the open position.However, if pressure in the reference chamber 324 is above thepredetermined reference magnitude, the reference spring bias force isovercome, and the regulator valve 310 is moved to the closed position.It will be appreciated that the bias force supplied by the referencespring 314 is preferably adjustable, to thereby adjust the pressuremagnitude at which the regulator valve 310 will close. In the depictedembodiment, the reference regulator 302 includes an adjustment nut 328that facilitates adjustment of the bias force.

Turning now to a description of the shuttle valve 304, it is seen thatthis component includes a housing 330 and a shuttle element 332. Theshuttle valve housing 330 includes three fluid ports—a first fluid port334, a second fluid port 336, and a third fluid port 338. The firstfluid port 334 is in fluid communication with the reference regulatoroutlet flow passage 318, the second fluid port 336 is in fluidcommunication with the valve body outlet port 216, and the third fluidport 338 is in fluid communication with the valve actuator 206.

The shuttle element 332 is disposed within the shuttle valve housing 330and is movable between a first position (shown in FIG. 3) and a secondposition (not shown). In the first position, the shuttle element 332fluidly couples the first fluid port 334 to the third fluid port 338,and isolates the second fluid port 336 from the first 334 and thirdfluid ports 338. In the second position, the shuttle element 332 fluidlycouples the second fluid port 336 to the third fluid port 338, andfluidly isolates the first fluid port 334 from the second 336 and third338 fluid ports.

The remaining portion of this starter air valve embodiment 300 thatdiffers from the previous embodiment is the bleed flow passage 306. Thebleed flow passage 306 is fluidly coupled between the actuation controlvalve housing fluid outlet port 282 and the rate control servo mechanismhousing control air inlet flow passage 244. In particular, the bleedflow passage includes an inlet port 340 that is fluidly coupled to boththe actuation control valve housing fluid outlet port 282 and the ratecontrol servo mechanism housing control air inlet flow passage 244, andan outlet port 342 that is vented to the surrounding environment. Ableed orifice 344 is disposed within the bleed flow passage 306, andrestricts the flow of pressurized air through the bleed flow passage306. The bleed orifice 344 is sized to not only limit pressurized airflow through the bleed flow passage 306, but additionally ensures thatthe pressure downstream of the regulator housing outlet flow passage 318does not exceed a predetermined pressure magnitude when the actuationcontrol valve 210 is energized.

As with the previous embodiment, having now described the starter airvalve 300 shown in FIG. 3 structurally, a description of the operationof the starter air valve 300 will now be provided. As before, thefollowing description is predicated on the flow control valve 204initially being in the closed position.

With the flow control valve 204 in the closed position, it is seen thatthe actuation control valve solenoid 272 is de-energized. With thesolenoid 272 de-energized, the valve 274 is in its first position, whichmeans the actuation control valve housing inlet flow passage 280 isfluidly isolated from the actuation control valve housing outlet flowpassage 282. As a result, the pressure in the reference pressure chamber324, and thus the reference regulator housing outlet flow passage 318and the shuttle valve housing first fluid port 334, approaches thepressure at the flow passage inlet port 214. This pressure issubstantially equivalent to that in the non-illustrated pressure source,and is greater than the pressure at the flow passage outlet port 216.Thus, as shown, the shuttle valve element 332 is in the first position,and the pressure in the actuator housing 218 aids the piston bias spring222 in urging the flow control valve 204 toward its closed position. Itwill additionally be appreciated that as the pressure in the referencepressure chamber 324 exceeds the predetermined reference magnitude, theregulator valve 310 will close, although this is not shown in FIG. 3.There will nonetheless be a small amount of leakage around the regulatorvalve 310.

When it is desired to open the flow control valve 204, to thereby permitfluid flow through the conduit 202, the actuation control valve solenoid272 is energized. When energized, the solenoid 272 moves the valve 274from the first position to the second position. If, as was noted above,the regulator valve 310 was closed due to the pressure in the referencechamber 324, this pressure is slowly relieved through the bleed airorifice 344, via the actuation control valve 210, thereby allowing theregulator valve 310 to open, and the reference regulator 302 to beginregulating air pressure downstream of the reference regulator housingoutlet flow passage 318.

With the regulator valve 310 in the open position, this allowspressurized air, at a regulated pressure magnitude, to flow through thereference regulator 302, into and through the actuation control valve210, and into the rate control servo mechanism control air inlet flowpassage 244. A portion of the regulated pressurized air that flowsthrough the actuation control valve 210 also continues to flow throughthe bleed air orifice 344. As before, because the poppet valve 238 isbiased toward its open position, the regulated pressurized air suppliedto the rate control servo mechanism control air inlet flow passage 244flows past the poppet valve 238, into and through the control air outletflow passage 252 and the snubbing orifice 260, and into the actuatorhousing 218. Because the area on the top side (relative to theperspective of FIG. 3) of the piston 220 is much greater than the areabelow the piston 220, the overall force on the actuator piston 220causes it to begin to move the flow control valve 204 toward the openposition. As a result, pressurized air from the non-illustratedpressurized air source flows into the flow passage 212 downstream of theflow control valve 204, and the downstream pressure begins to increase.

As the pressurized air begins flowing into the flow passage 212downstream of the flow control valve 204, some of the pressurized airflows back to the rate control servo mechanism 208, via the feedbackinlet flow passage 248. A portion of this pressurized air is alsodirected into the shuttle valve 304, via the shuttle valve housingsecond fluid port 336. The overall operation of the rate control servomechanism 208 in this embodiment 300 is the same as in the previousembodiment 200, thus its operation hereafter will not be reiterated.When the pressure magnitude of the pressurized air downstream of theflow control valve 204 exceeds the pressure magnitude of the regulatedpressurized air flowing into the shuttle valve housing first fluid port334, the shuttle element 332 is moved from the first position to thesecond position. Thus, the shuttle valve housing third fluid port 338 isfluidly coupled to the second fluid port 336, which means the downstreamair pressure is now acting on the bottom side of the actuator piston220. This pressure, in combination with the piston bias spring 222,supplies a closing force that urges the actuator piston 220 to move theflow control valve 204 toward the closed position. The closing force iscounteracted by the opening force generated by the pressure of theregulated pressurized air supplied to the top side of the actuatorpiston 220 via the rate control servo mechanism 208.

As long as the actuation control valve 210 remains energized, thecombination of the closing and opening forces will continue acting onthe actuator piston 220. Together, these forces act to position the flowcontrol valve 204 so that the pressure downstream of the flow controlvalve 204 is regulated to a predetermined magnitude. For example, ifdownstream pressure increases above the predetermined magnitude, theflow control valve 204 is moved toward its closed position, reducingflow through the flow passage 212 and causing downstream pressure tobegin decreasing. As the downstream pressure begins decreasing, theclosing force generated thereby concomitantly decreases, causing theflow control valve 204 to move open further and downstream pressure toincrease.

When it is desired to close the starter air valve 300, its operation issimilar to that of the previously described embodiment 200. Inparticular, the actuation control valve solenoid 272 is firstde-energized, which allows the solenoid bias spring 278 and the valvebias spring 276 to move the valve 274 to the first position. With thevalve 274 in the first position, the bleed flow passage 340 is fluidlyisolated from the reference regulator 302. However, the bleed flowpassage 340 remains fluidly coupled to the rate control servo mechanismhousing control air inlet flow passage 244. Because the poppet valve 238is biased toward its open position, the control air outlet flow passage252 and thus the actuator housing 218 are fluidly coupled to the bleedflow passage 340. Thus, the regulated control air in the actuatorhousing 218 is vented to atmosphere via the bleed flow passage 340. Thisreleases the pressure on the top side of the actuator piston 220 and,assisted by the force of the downstream pressure on the bottom side ofthe actuator piston and the actuator bias spring 222, causes theactuator 206 to move the flow control valve 204 to the closed position.When the flow control valve 204 closes, the downstream pressuremagnitude decreases. When the regulated pressure at the shuttle valvehousing first fluid port 334 exceeds the downstream pressure, theshuttle valve element 332 returns to the first position, and the starterair valve 300 returns to the configuration shown in FIG. 3.

The starter air valve 300 described above and depicted in FIG. 3 ismerely exemplary of a particular embodiment of a regulating valveconfiguration. Various other configurations could also be used toimplement the regulating valve embodiment. For example, the starter airvalve 300 could be implemented by transposing the positions of thereference regulator 302 and the actuation control valve 210, and notincluding the shuttle valve 304 and the flow passages associatedtherewith.

The starter air valves 200, 300 are, for ease of explanation, depictedherein schematically. It will be appreciated that the components thatmake up the starter air valves 200, 300, while illustrated as individualcomponents fluidly coupled by individual flow passages, are preferablyphysically configured together as a single valve assembly. However, itwill be additionally appreciated that the starter air valves 200, 300could, if desired, be constructed and physically implemented asindividual, spaced-apart components, as illustrated in the schematicrepresentations.

The starter air valves 200, 300 depicted and described herein areconfigured to provide improved opening characteristics relative topresently known valves. The configuration of the disclosed valves 200,300 additionally compensates for piston seal or diaphragm leakage thatmay occur in the actuator 206. Moreover, the valves 200, 300 willcontinue to operate even if relatively large amounts of piston seal ordiaphragm leakage occurs.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt to a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe appended claims.

1. A starter air valve assembly, comprising: a valve body defining aflow passage having at least an inlet port and an outlet port; a valvedisposed at least partially within the flow passage and moveable betweenan open position and a closed position; a rate control servo mechanismadapted to receive pressurized fluid and configured, upon receiptthereof, to supply a controlled flow of the pressurized fluid; and avalve actuator coupled to the valve and in fluid communication with therate control servo to thereby receive the controlled flow of thepressurized fluid, the valve actuator configured, upon receipt of thecontrolled flow of the pressurized fluid, to move the valve between theclosed position and the open position at a substantially controlledrate.
 2. The valve assembly of claim 1, further comprising: an actuationcontrol valve housing having a fluid inlet adapted to receivepressurized fluid and a fluid outlet in fluid communication with therate control servo mechanism; and an actuation control valve mountedwithin the actuation control valve housing and moveable between a firstposition, in which the actuation control valve housing fluid inlet isfluidly isolated from the actuation control valve housing fluid outlet,and a second position, in which the actuation control valve housingfluid inlet is fluidly coupled to the actuation control valve housingfluid outlet, to thereby supply pressurized fluid to the rate controlservo mechanism.
 3. The valve assembly of claim 2, further comprising: asolenoid coupled to the actuation control valve, the solenoid adapted toreceive an electrical signal and operable, in response thereto, to movebetween a first position and a second position, to thereby move theactuation control valve between the first and second positions,respectively.
 4. The valve assembly of claim 2, further comprising: areference regulator having a fluid inlet and a fluid outlet, the fluidinlet adapted to couple to a pressurized fluid source, the fluid outletfluidly coupled to the actuation control valve housing fluid inlet, thereference regulator configured to selectively supply pressurized fluidto the actuation control valve housing fluid inlet at a substantiallyconstant, regulated pressure.
 5. The valve assembly of claim 4, furthercomprising: a bleed flow passage having an inlet port and an outletport, the bleed flow passage inlet port fluidly coupled to the actuationcontrol valve housing fluid outlet port; and a bleed orifice disposedwithin the bleed flow passage.
 6. The valve assembly of claim 5, whereinthe bleed orifice is sized so that the substantially constant, regulatedpressure does not exceed a predetermined pressure magnitude.
 7. Thevalve assembly of claim 4, further comprising: a shuttle valve housinghaving a first fluid port in fluid communication with the referenceregulator fluid outlet, a second fluid port in fluid communication withthe flow passage outlet port, and a third fluid port in fluidcommunication with the valve actuator; and a shuttle element disposedwithin the shuttle valve housing and movable between at least a firstposition, in which the shuttle element fluidly isolates the first fluidport from the third fluid port, and a second position, in which theshuttle element fluidly isolates the second fluid port from the thirdfluid port.
 8. The valve assembly of claim 2, further comprising: areference regulator having a fluid inlet and a fluid outlet, the fluidinlet fluidly coupled to the actuation control valve housing fluidoutlet, the fluid outlet fluidly coupled to the rate control servomechanism, the reference regulator configured to selectively supplypressurized fluid to the rate control servo mechanism at a substantiallyconstant, regulated pressure.
 9. The valve assembly of claim 1, whereinthe rate control servo mechanism comprises: a housing defining at leasta first chamber and a second chamber; a diaphragm disposed between thefirst and second chambers and fluidly isolating the first and secondchambers from one another; a control air flow passage extending throughthe housing and having at least an inlet port and an outlet port, thecontrol air flow passage inlet port adapted to receive the pressurizedfluid, and the control air flow passage outlet port fluidly coupled tothe valve actuator; a pre-charge flow passage coupled to the housing andhaving at least an inlet port and an outlet port, the pre-charge flowpassage inlet port fluidly coupled to the control air flow passage, andthe pre-charge flow passage outlet port in fluid communication with thesecond chamber; a feedback flow passage coupled to the housing andhaving at least an inlet port and an outlet port, the feedback flowpassage inlet port fluidly coupled to the flow passage outlet port, andthe feedback flow passage outlet port in fluid communication with thesecond chamber; a rate control flow passage coupled to the housing andhaving at least an inlet port and an outlet port, the rate control flowpassage inlet port fluidly coupled to the feedback flow passage outletport, and the rate control flow passage outlet port in fluidcommunication with the first chamber; a check valve disposed within thefirst chamber and configured to selectively fluidly isolate thepre-charge orifice outlet port from the second chamber; and a ratecontrol valve disposed within the housing and coupled to the diaphragm,the rate control valve movable between a closed position, in which thecontrol air flow passage inlet port is fluidly isolated from the controlair flow passage outlet port, and an open position, in which the controlair flow passage inlet port is fluidly coupled to the control air flowpassage outlet port.
 10. The valve assembly of claim 8, furthercomprising: a pre-charge orifice disposed within the pre-charge flowpassage; a feedback orifice disposed within the feedback flow passage;and a rate control orifice disposed within the rate control flowpassage.
 11. The valve assembly of claim 9, wherein the pre-charge,feedback, and rate control orifices are sized relative to one another tocontrol a differential pressure between the first and second chambers,to thereby control movement of the rate control valve between the openposition and the closed position, whereby the flow of pressurized fluidto the valve actuator is controlled.
 12. A rate control servo mechanismfor controlling a rate of movement of a valve, the mechanism comprising:a housing defining at least a first chamber and a second chamber; adiaphragm disposed between the first and second chambers and fluidlyisolating the first and second chambers from one another; a control airflow passage extending through the housing and having at least an inletport and an outlet port, the control air flow passage inlet port adaptedto receive a flow of pressurized fluid, and the control air flow passageoutlet port fluidly coupled to the valve actuator; a pre-charge flowpassage coupled to the housing and having at least an inlet port and anoutlet port, the pre-charge flow passage inlet port fluidly coupled tothe control air flow passage, and the pre-charge flow passage outletport in fluid communication with the second chamber; a feedback flowpassage coupled to the housing and having at least an inlet port and anoutlet port, the feedback flow passage inlet port adapted to fluidlycouple to a flow duct, and the feedback flow passage outlet port influid communication with the second chamber; a rate control flow passagecoupled to the housing and having at least an inlet port and an outletport, the rate control flow passage inlet port fluidly coupled to thefeedback flow passage outlet port, and the rate control flow passageoutlet port in fluid communication with the first chamber; and a ratecontrol valve disposed within the housing and coupled to the diaphragm,the rate control valve movable between a closed position, in which thecontrol air flow passage inlet port is fluidly isolated from the controlair flow passage outlet port, and an open position, in which the controlair flow passage inlet port is fluidly coupled to the control air flowpassage outlet port.
 13. The mechanism of claim 12, further comprising:a check valve disposed within the first chamber and configured toselectively fluidly isolate the pre-charge orifice outlet port from thesecond chamber;
 14. The mechanism of claim 12, further comprising: apre-charge orifice disposed within the pre-charge flow passage; afeedback orifice disposed within the feedback flow passage; and a ratecontrol orifice disposed within the rate control flow passage.
 15. Themechanism of claim 14, wherein the pre-charge, feedback, and ratecontrol orifices are sized relative to one another to control adifferential pressure between the first and second chambers, to therebycontrol movement of the rate control valve between the open position andthe closed position, whereby the flow of pressurized fluid to the valveactuator is controlled.
 16. The mechanism of claim 12, wherein the ratecontrol valve comprises a poppet valve.
 17. The mechanism of claim 12,further comprising: a back plate coupled to the rate control valve andthe diaphragm; and a spring disposed within the first chamber andcoupled between the housing and back plate, the spring configured tobias the rate control valve toward the open position.
 18. An air turbinestarter, comprising: a turbine housing having a fluid inlet port, afluid outlet port, and a fluid flow passage extending therebetween; aturbine wheel having a turbine shaft rotationally mounted within theturbine housing, the turbine wheel further having at least two turbineblades extending radially into the fluid flow passage; and a starter airvalve assembly coupled to the turbine housing, the starter air valveassembly including: a valve body defining a flow passage having at leastan inlet port and an outlet port, the flow passage inlet port adapted toreceive a flow of pressurized air, the flow passage outlet port in fluidcommunication with the turbine housing fluid inlet port, a flow controlvalve disposed at least partially within the flow passage and moveablebetween an open position and a closed position; a rate control servomechanism adapted to receive pressurized fluid and configured, uponreceipt thereof, to supply a controlled flow of the pressurized fluid;and a valve actuator coupled to the valve and in fluid communicationwith the rate control servo to thereby receive the controlled flow ofthe pressurized fluid, the valve actuator configured, upon receipt ofthe controlled flow of the pressurized fluid, to move the flow controlvalve between the closed position and the open position at asubstantially controlled rate, whereby the turbine housing fluid inletport is fluidly isolated from and fluidly coupled to, respectively, theflow passage inlet port.
 19. In a valve assembly including a valve bodydefining a flow passage therethrough, a flow control valve mounted onthe valve body, and a fluid-operated actuator coupled to the flowcontrol valve, a method of opening the flow control valve, comprisingthe steps of: supplying pressurized fluid to the fluid-operated actuatorto generate an opening force that begins opening the flow control valve,whereby pressurized fluid may flow through the valve body flow passage;in response to fluid flow through the valve body, intermittentlysupplying the pressurized fluid to the actuator to therebyintermittently generate the opening force at a controlled rate, wherebythe flow control valve further opened at a controlled rate.